The present invention relates to propelling drive control apparatus for a working vehicle comprising a hydraulically operable clutch for providing a drive transmission state, and a control valve for controlling the clutch.
In a known working vehicle as noted above, the clutch is operable by the control valve to allow a change speed operation and a backward and forward drive switching operation. Where half-clutch drive and sudden start of the vehicle are desired known working vehicle of this type includes s friction clutch in addition to the hydraulically operable clutch for effecting the change speed operation and the backward and forward drive switching operation, as disclosed in Japanese Patent Publication Kokai No. 57-87717 for example. This friction clutch is operable to provide for the sudden start of the vehicle as well as the half clutch drive for realizing slow start of the vehicle or for pulling the vehicle out of a soft, wet ground.
The known vehicle thus requires the two separate clutches, one operable by the control valve to allow the change speed operation and the backward and forward drive switching operation and the other for realizing the sudden start and the half-clutch drive of the vehicle. This is unsatisfactory from the points of view of construction and cost.